WO2010051866A1 - Process and apparatus for producing a moulding with a decorative surface - Google Patents

Abstract

The present invention relates to a process for producing a moulding 7 with a decorative surface 5 by the in-mould lamination, using a compression-moulding or injection-compression-moulding method, of a foil which is inserted into a mould and consists of thermoplastic. In this process, the embossed structure which is depicted in the form of a negative on the inner surface 4 of a mould die 2 is transferred onto the decorative foil in a thermal embossing step.

Description

Method and device for producing a molded part with decorative surface

The invention relates to a method for producing a molded part with decorative surface having the features of the preamble of claim 1.

The invention also relates to a device for producing a molded part with decorative surface having the features of the preamble of claim 7.

Generic plastic molded parts, in particular interior trim parts for motor vehicles, are today usually produced by placing a decorative material in a mold and then back-injecting, back-pressing or back-pressing with a thermoplastic.

DE 198 51 117 C2 describes a method for producing a molded part by insert molding or backpressing a decorative material having a structured surface, wherein a tool is used which has a surface structure on its surface which comes into contact with the decorative material Negative corresponds to the desired surface structure of the decorative material. When pressing or injecting the desired surface structure is now embossed the decorative material. In doing so, the prag- on pattern of the tool exceeds the original surface structure of the decor material, with the risk that the visual appearance of the decor suffers.

DE 101 13 272 A1 describes a process for the production of plastic moldings which are coated with decorative materials

BESTÄTIGUNGSKOPIH are, whereby decor materials are used, which are already structured and whose surface is no longer coined in the tool itself. In order to avoid damage to the decorative material during injection molding or pressing, the melt pressure is kept low when entering the tool and additional measures are taken after the molding process to preserve the surface quality. The method described in DE 101 13 272 Al is particularly suitable for leather as a decorative material.

DE 10 2005 043 180 A1 describes a process for producing a shaped body which is constructed from a carrier layer whose surface is at least partially coated with a grained film. For this purpose, an unhardened film is inserted into a tool whose surface has the negative of the applied scars. When backing with the backing material, the foil is now printed in the negative of the scars of the tool. Since the film combines simultaneously with the plastic of the plastic carrier layer, the grain structure persists after the carrier layer has solidified. In order to support the formation of the scars in the film, a vacuum can be applied between the film surface and the embossing surface of the molding tool.

In DE 37 42 457 Al a manufacturing method for plastic moldings is described with decorative embossed surface coating in which a ungepragte thermoformable film is placed in a mold that has on its inner surface at least partially a Pragestruktur. Subsequently, a molten thermoplastic material is injected into the mold. At the same time or following the injection of the molten thermoplastic material is injected by injection of a gas in the Plastic melt additional pressure built up, which is maintained at least until the partial solidification of the thermoplastic material. As a result, the surface film is embossed uniformly and durably at the same time as the injection molding of the core material.

The direct Hinterformen of decorative materials in the mold with a thermoplastic carrier material has as a one-step process for the production of moldings with decorative surface, although compared to the previously used two-stage

Processes in which the molding was laminated with the decorative skin after molding, the advantage that it is much less expensive, but it is often difficult due to the pressure and temperature conditions in the mold, the embossing correctly and optically perfect from the negative of the embossing layer to transfer the decorative foil.

Frequently, the process is attempted to be improved by heating the unembossed raw film prior to insertion into the mold, so that the film more easily assumes the contours of the stamping layer during the subsequent molding in the mold. However, the previous heating of the film has the disadvantage that the film is very soft, whereby their handling is difficult. This often leads to drape, whereby the optical quality of the decorative surface suffers. In addition, the decorative film often cools down to the point of contact with the tool surface, so that optimal impression of the film on the tool surface is no longer possible. This also leads to the plastic film being pressed unevenly against the tool wall.

Further optimization of the impression of the tool surface on the decorative film can be achieved by partially heating the mold surface. partial tool done. This possibility is described, for example, in DE 37 42 457 A1. The disadvantage of the method described in the above-mentioned document, however, is that a complete heating of the entire mold takes place, which is not only a relatively slow process, but is also associated with a high expenditure of energy. In addition, such processes usually use water vapor, water or oil as the heating or cooling medium, which are relatively slow heat transfer media confined to the maximum temperature.

Thus, there is still the problem of finding a simple method for optically perfect transfer of the embossing or structure of a surface of the molding tool, which is provided as a negative for the desired surface structure of the decorative material, to the decorative surface.

The problem is solved by a method having the features of claim 1. Advantageous embodiments of the inventive method are the subject of the corresponding subclaims.

The subject matter of the present invention is also an apparatus for the production of a molded part with decorative surface, with which the method according to the invention is carried out. This object is achieved by a device having the features of claim 7. Advantageous embodiments of the device are the subject of the corresponding subclaims.

The inventive method is based on the fact that an initially unstructured, consisting of a thermoplastic plastic film is placed in a mold die, which on its inner surface as a negative for the De- Has koroberflache trained embossed structure. In the molding process, the structure of the inner surface of the molding die is then transferred to the decorative film in a thermal embossing step. This process is carried out with the tool closed and the foil can be molded or back-pressed simultaneously or subsequently with a thermoplastic. After the subsequent cooling of the mold, the molding can be removed from the mold and removed from the mold.

In the thermal embossing step, the inserted film is heated to almost its melting temperature and softens thereby, so that it ideally adapts to the embossing pattern of the molding die. The heating of the decorative foil takes place by means of a contour-near electrical heating element. Either the structured inner surface of the molding die is either itself combined with a contour-near heating element, or a contour-near heating element is integrated in the immediate vicinity of the inner surface of the molding die.

In an advantageous embodiment of the present invention, the inner surface of the mold die is formed as part of an induction heater. This embodiment of the invention allows the mold surface can be heated within a very short time, without having to heat the entire mold.

Compared with known methods, in which close-to-contour temperature control channels are provided, for example, in the immediate vicinity of the surface, which are tempered with steam, water or oil, the method according to the invention has the advantage that the energy transfer takes place more rapidly and, in addition, higher temperatures. can be achieved. In addition, the formation of conformal temperature control channels is associated with a relatively high technical complexity, whereby the mold would be more expensive.

A further advantageous embodiment of the present invention provides that in the mold die in the immediate vicinity of the patterned surface of the mold contour near resistance heating is provided, with the help turn very quickly targeted the structured surface of the mold die can be heated, the adjacent decorative film is heated so far in that it adapts ideally to the embossing structure of the surface of the mold die.

The main advantage of the two above-described embodiments of the invention over the previously used methods is that very short heating times and high temperatures can be realized, whereby the cycle times significantly reduced and thus the component costs can be reduced and improves the optical quality of the transfer of the embossed structure becomes.

The inventive method can be used particularly advantageously in connection with the injection molding, wherein, for example. An unhardened film is placed in an injection mold on a formative surface and there is briefly heated prior to injection of the thermoplastic material, whereby the film of the graining of the embossing surface adapts , The film is heated superficially by the hot mold wall to the optimum temperature for molding the grain. Preheating the foil is no longer necessary. To get air bubbles between the foil and the tool wall To prevent additional ventilation holes can be provided outside the visual contour, whereby the risk of wrinkling is further reduced.

A further advantageous embodiment of the method according to the invention provides that the film is warmed prior to insertion into the tool to facilitate insertion into the tool. For this purpose, however, the film must now be heated only slightly and brought to a temperature which allows a rough adaptation to the tool contour, so that the handling of the film itself does not pose a problem, while the actual heating of the film to adapt to the embossing pattern in Tool itself is done.

A similar positive effect can be achieved by the fact that the film is already at least roughly adjusted before insertion into the mold by preforming the geometry of the mold or of the molded part to be produced, so that a close-contour insertion of the film is facilitated in the mold. In this case, then a preheating of the film is no longer necessary, but can be integrated as an additional facilitation of production in this step.

The subject matter of the present invention is also a device for the production of molded parts with a decorative surface, wherein the device consists of a molding tool with a mold core and a mold die and the inner surface of the mold template is provided with an embossing pattern designed as a negative for the decorative surface. In the forming die itself, a contour-near heating element is integrated in the region of the inner surface, with the aid of which the surface of the die can be heated at extremely low heat-up times, whereby the transmissive surface is then heated. A pragestruktur example. Is facilitated on an inserted thermoplastic film. The method is suitable not only for injection molding with thermoplastics, but also generally for the Hinterpragen and pressing back with thermoplastics.

Both for injection molding as well as for the Hinterpragen and Hinterpressen the usual thermoplastic materials such. As polypropylene, polyethylene, polystyrene, acrylonitrile butadiene styrene, polycarbonate, polyvinyl chloride, polymethyl methacrylate and polyethylene terephthalate or copolymers thereof are used, which can be used in advantageous embodiments in addition to the stabilization of the molding fibers.

As a film material is particularly suitable polypropylene, polyethylene or polyvinyl chloride.

After the forming process, the tool is cooled and the molding can be removed from the mold once it has cooled sufficiently to be dimensionally stable. The cooling itself is done by conventional Kuhlbohrungen, which are flowed through by a conventional Kuhlmittel.

In the following the invention will be explained in detail by means of illustrations. Show

1 shows a cross section through a mold with an inductively heated inner Matrizenoberflache and

Fig. 2 shows a cross section through a mold with an integrated electrical resistance heater. FIG. 1 shows the section through a molding tool 1 which is constructed from a molding die 2 and a molding tool core 3. The inner surface 4 of the molding tool 2 has an embossing structure which is formed as a negative to the structure of the surface of the decorative film 5. The mold die 2 is combined with an inductive heater 10, with the aid of which the inner die surface 4 can be heated. In the molding die 2, additional vacuum channels 12 are arranged, which serve to remove the air possibly trapped between the inserted decorative film and the die surface 4, in order to avoid wrinkling of the decorative film in this way. In addition, the mold die 2 cooling channels 8, which are flowed through after the shaping process with cooling medium to accelerate the solidification of the molding 7.

Also in the mold core 3, the counterpart to the mold die 2, cooling channels 8 are arranged. In addition, an injection channel 11 for the thermoplastic synthetic material can be seen in the middle of the mold core 3.

Between mold core 3 and mold die 2, a finished molded part 7 is shown, which is constructed from a carrier 6 and the decorative surface 5.

FIG. 2 likewise shows in cross section an embodiment of a molding tool 1 in which the inductive heating is replaced by an electrical resistance heater 9, which is arranged in the edge region of the molding die 2 in the immediate vicinity of the structured surface 4. In the present embodiment, a plurality of heating elements 9 are provided, which are integrated into the mold die. Again, cooling channels 8 in the molding tool matrix are again ze 2 arranged, which are flowed through during cooling of the mold with a Kuhlmedium. In the illustration selected in FIG. 2, no vacuum channels are provided, which does not mean, however, that an embodiment with resistance heating would oppose an arrangement of vacuum channels in the molding die. Also in this embodiment can be easily integrated if required vacuum channels.

The finished molded part 7 and the mold core 3 correspond to the representation selected in FIG.

The particular advantage of the present invention over the prior art is that a decorative film which is to be superficially structured can be heated extremely quickly in the corresponding molding tool and thus adapted to a stamping structure of the molding surface of the molding tool. Thus, the cycle times for the production of molded parts can be significantly shortened, which leads to a corresponding cost reduction.

In addition, the quality of the transfer of the structure is improved by the rapid heating of the decorative film to sufficiently high temperatures to near the melting point of the plastic, so that the visual appearance of a molded article produced by the inventive method also has advantages over a conventional molding.

The inventive method for transferring a grain structure can be used particularly advantageously in order to give the surface of the component the appearance of a leather decoration. Reference sign list

1 mold

2 mold tools

3 mold tool core

4 inner surface of the molding die

5 decorative surface

6 carriers

7 molding

8 cooling channel

9 resistance heating

10 induction heating

11 injection channel

12 vacuum channel

Claims

claims 1. A method for producing a molded part (7) with a decorative surface (5) by Hinterformen, Hinterpragen or Hinterpressen a in a mold (1) inserted, consisting of a thermoplastic plastic film, one as a negative on the inner surface (4) of a Mold film (2) is transferred to the film in a thermal pragging step while the film is simultaneously molded or subsequently overmolded, backed or pressed with a thermoplastic, and wherein the molded article (7) is cooled after the mold (1) is subsequently cooled ) and removed from the forming tool (1), since it indicates that the film loaded in the forming tool (1) is heated to near melting temperature before or during the forming, backpressing or backpressing, the heat being transferred to the mold Foil over the heating element with a near-contour heating element (9, 10) heated inner surface (4) of the mold die (2) takes place. 2. Method according to claim 1, characterized in that the inner surface (4) of the molding die (2) is inductively heated. 3. The method according to claim 1, characterized in that the heating of the inner surface (4) of the molding die (2) takes place by means of an electrical resistance heater (9) integrated in the immediate vicinity of the surface (4). 4. Method according to one of claims 1 to 3, characterized in that the air enclosed between the tool surface (4) and the film is sucked off via suction channels (12) arranged in the molding tool die (2). 5. The method according to any one of claims 1 to 4, d a d u r c h e c e n e c e s in that the film is heated prior to insertion into the tool (1). 6. Method according to one of claims 1 to 5, characterized in that the film is already adapted to the geometry of the molding tool (1) by preforming. 7. A device for producing a molded part (7) with decorative surface (5) consisting of a molding tool (1) with a mold core (3) and a mold die (2), wherein the inner surface (4) of the mold die (2) a stamping structure designed as a negative for the decor surface (5), characterized ge kenn zei chnet, as ss a near-contour heating element (9, 10) for electrically heating the mold surface (4) is provided. 8. Device according to claim 7, characterized in that the inner surface (4) of the molding die (2) is combined with an induction heater (10). 9. Apparatus according to claim 7, characterized in that an electrical resistance heater (9) is arranged in the mold die (2) in the immediate vicinity of its inner surface (4). 10. Device according to one of claims 7 to 9, since in the die mold (2) suction channels (12) are arranged for sucking the air entrapped between the inserted film and the surface (4) of the mold die (2).